Certain undesirable physiological manifestations, such as acne vulgaris, seborrhea, female hirsutism, androgenic alopecia which includes female and male pattern baldness, and benign prostatic hyperplasia, are the result of hyperandrogenic stimulation caused by excessive accumulation of testosterone ("T") or similar androgenic hormones in the metabolic system. Androgenic alopecia is also known as androgenetic alopecia. Early attempts to provide a chemotherapeutic agent to counter the undesirable results of hyperandrogenicity resulted in the discovery of several steroidal antiandrogens having undesirable hormonal activities of their own. The estrogens, for example, not only counteract the effect of the androgens but have a feminizing effect as well. Non-steroidal antiandrogens have also been developed, for example, 4'-nitro-3'-trifluoromethyl-isobutyranilide. See Neri, et al., Endocrinol. 1972, 91 (2). However, these products, though devoid of hormonal effects, compete with all natural androgens for receptor sites, and hence have a tendency to feminize a male host or the male fetus of a female host and/or initiate feed-back effects which would cause hyperstimulation of the testes.
The principal mediator of androgenic activity in some target organs, e.g. the prostate, is 5.alpha.-dihydrotestosterone ("DHT"), formed locally in the target organ by the action of testosterone-5.alpha.-reductase. Inhibitors of testosterone-5.alpha.-reductase will serve to prevent or lessen symptoms of hyperandrogenic stimulation in these organs. See especially U.S. Pat. No. 4,377,584, issued Mar. 22, 1983, and U.S. Pat. No. 4,760,071, issued Jul. 26, 1988, both assigned to Merck & Co., Inc.
The enzyme 5.alpha.-reductase catalyzes the reduction of testosterone to the more potent androgen, dihydrotestosterone, as shown below: ##STR2##
Finasteride, (17.beta.-(N-tert-butylcarbamoyl)-3-oxo-4-aza-5.alpha.-androst-1-ene-3-one ) as shown below, is a potent inhibitor of the human prostate enzyme. ##STR3## Under the trade name PROSCAR.RTM., finasteride is known to be useful in the treatment of hyperandrogenic conditions; see eg. U.S. Pat. No. 4,760,071. Finasteride is currently prescribed for the treatment of benign prostatic hyperplasia (BPH), a condition afflicting to some degree the majority of men over age 55. Finasteride's utility in the treatment of androgenic alopecia and prostatic carcinoma is also disclosed in the following documents: EP 0 285,382, published Oct. 5, 1988; EP 0 285,383, published Oct. 5, 1988; Canadian Patent no. 1,302,277; and Canadian Patent no. 1,302,276.
There are two isozymes of 5.alpha.-reductase in humans. One isozyme (type 1 or 5.alpha.-reductase 1) predominates in sebaceous glands of facial and skin tissue and is relatively insensitive to finasteride (see, e.g., G. Harris, et al., Proc. Natl. Acad. Sci. USA, Vol. 89, pp. 10787-10791 (November 1992)); the other (type 2 or 5.alpha.-reductase 2) predominates in the prostate and is potently inhibited by finasteride.
Since 5.alpha.-reductase and its isozymes convert testosterone to DHT, inhibition of either or both of the isozymes would serve to alleviate the conditions and diseases mediated by DHT. The present invention addresses this by providing novel compounds that are active as inhibitors of 5.alpha.-reductase.